It is currently widespread that users access a server having a function of an access point in a wireless local area network (LAN), and download an application program (hereinafter, also referred to as an “application”) from the server to their mobile devices for use as occasion calls. For example, there are cases where when a user visits a store, or the like, the user downloads an application using a smart phone, a tablet terminal, or the like “on the spot”, and uses the application.
In the case of a device that is connected to a cloud computer through the Internet, if the device is stolen, it is possible to lock the device by control data transmitted from the cloud computer to the device, or to delete storage data in the device. However, in the case of a device that does not have a connection function to the Internet, the device is not capable of obtaining the control data, and thus it is difficult to protect the device by the above-described method, and to avoid leakage of internal information.
Thus, a method of encrypting storage data in a device is provided as another countermeasure against the case where the device is stolen. However, in this method, a user has to manage the same number of decryption passwords as the number of the devices, and thus there is a problem in that it takes much time and effort.
As another countermeasure against the case where a device is stolen, Japanese Laid-open Patent Publication No. 2013-258650 has proposed an anti-theft featured communication terminal in which whether a radio communication server is located in a predetermined communication range or not is detected from a communication state of the radio communication, and if not located within the communication range, a warning is output.